Use of probiotic bacteria in the rearing of Senegalese sole (Solea senegalensis) larvae

Three candidate probiotics, which had shown antimicrobial activity in vitro against two fish pathogens, were used in the rearing of Senegalese sole larvae and postlarvae. These probiotics improved the survival of starved sole yolk-sac larvae. A feeding experiment of sole larvae and postlarvae comprised three treatments: A, B and C. Cultures of a Vibrio sp. (2J18) were added to treatment A, whereas a gram-positive (J84) and a Shewanella sp. strain (2J27), were added to treatment B, while in a control treatment C no bacteria were added. Addition of bacteria in treatment B increased survival of larvae in the first phase of the experiment [0-20 days after hatching (DAH) (P < 0.05)] and decreased the numbers of colony-forming units (CFU) in larval gut 5 DAH compared with the control treatment (P < 0.05). No differences were observed in survival (25-47%) during the second phase of the experiment (20-60 DAH). Nevertheless, the total numbers of CFU in fish gut 40 DAH were significantly lower in treatment B (P < 0.05). The colonization rates of the added bacteria were the highest 5 and 11 DAH, and the highest average values reached were 65%, 82% and 17% of the total CFU count for the strains 2J18, 2J27 and J84 respectively.